The goal of this proposal is to determine ion channel localization and Ca 2+ buffering capacity of the cilia of olfactory neurons. Ion channels often have spatial arrangements within compartments of sensory neurons that dictate their timing and degree of activation. Olfactory neurons have narrow extensions called cilia, which contain a high density of ion channels. These ion channels, the cyclic-nucleotide-gated (CNG) channel, and the Ca2+ activated Cl- channel, are activated sequentially during an odor response. Ca2+ from the CNG channel activates the Cl- channel. The distribution of the two channel types in the ciliary membrane may dictate their relative timing of activation. It may also influence the amplitude of the response for the neuron, as a signal from the distal region of the cilium may diminish before it reaches the dendrite. Ca2+ buffering regulates processes in other sensory neurons by limiting the rate and range of Ca2+ diffusion from Ca2+ channels. In olfactory neurons, spatial arrangements and Ca2+ buffering may introduce a threshold CNG current for amplification. A biophysical model will be used to make predictions about these two properties of the cilium. These predictions will be tested with patch clamp experiments. [unreadable] [unreadable]